Compressible Streamline-Based Simulation With Changes in Oil Composition

Abstract

Summary In Brazil, there are several offshore oil fields with horizontal oil-density variations. API tracking, which is available in some commercial finite difference simulators, can deal with such cases by allowing the definition of an initial oil-gravity distribution and tracking variations of oil density owing to the movement of oil. Streamline-based simulators can be much faster than conventional finite-difference simulators when applied to large and heterogeneous models. However, this approach is most accurate and efficient when it is assumed that the rock and fluids are incompressible. In previous work, Beraldo et al. (2007) presented an incompressible formulation for streamline simulation with an API tracking option using two components in the oleic phase. This paper presents a compressible formulation for streamlines that also considers API tracking. It has an approach similar to the one presented by Cheng et al. (2006) and Osako and Datta-Gupta (2007). However, cumulative volume is used in the streamline solution, instead of time of flight, which reduces mass-conservation errors. The method was implemented in a 3D two-phase streamline-based simulator. Tests based on a Brazilian oilfield model demonstrate that the implementation can reproduce the results of a conventional simulator, even when significant liquid compressibilities are considered. Another test, using the SPE 10th Comparative Case, indicates that it can be substantially faster for finely resolved models.